The present invention relates to a method of filtering a fluid flowing from a fluid supply duct in a first direction through a filtering medium into a fluid discharge duct.
The fluid to be filtered may be a gaseous fluid of any type, such as combustion gas, air, and gases for medical and industrial use. However, the invention particularly relates to filtering a liquid fluid, such as liquid solvents, cleaning fluids, and fluids used in industrial processes. More particularly, the invention relates to filtering of water or aqueous fluids, such as waste water, sea water, lake water or tap water.
In filtering fluids two principally different methods may be used. According to the first method the fluid is filtered by means of a replaceable filter, for example a filter cartridge, which is replaced by a new filter, when it has been more or less clogged up by the solid particles separated from the fluid. In the other known method the solid particles separated form the fluid and adhering to the filtering medium is continuously or intermittently released from the filtering medium. This may be done by imparting a shaking movement to the filtering medium and/or by temporarily reversing the fluid flow through the filtering medium so as to obtain a back-flush.
The first mentioned known method requiring rather frequent replacement of the filter or filter cartridge is rather costly, and the other known method described above requires special accessories and a special power source for operating the same.